Abstract: Given the trajectory of the welfare state whose origin refers to the European continent with diffusion and institutionalization after World War II and using the theoretical formulations of Gosta Esping-Andersen, Danish sociologist who attributes the emergence of the welfare state to the unfolding of historical and political factors such as class struggle, the structures of political power and institutional structures , this dissertation aims to reconstruct the ethical-political and philosophical principles of the Nordic welfare state called by Esping-Andersen in reason of his political conception of social-democratic Welfare State. The reconstruction of the theoretical debate in the nineteenth century among the scientific socialists and revisionists highlights Eduard Bernstein how theoretical of the Social Democratic Germany Party and exponent of revisionism. The second chapter investigates the postwar period in which social democracy has adopted the dictates of Keynesian economic policy and assumed social policies as a means of electoral mobilization and possible improvements of the living conditions of the population at the expense of a broader project of social transformation. The third chapter describes , based on the theories of Esping - Andersen and Peter Baldwin, the situation of the Scandinavian countries, which materialized the " social democratic model" of welfare state. Possession of more homogeneous occupational hazards led to the decision by the bourgeoisie of universalizing social policies in the nineteenth century to the Nordic countries. In the following century the mobilization of the Social Democratic Party in the Scandinavian countries kept doubly universalism to reflect the interests of the lower classes and the middle class. Thus, the particular conditions that define the Scandinavian countries (among them high occupational homogeneity) makes the success of this "social democratic model" irreproducible in other countries